a) Field of the Invention
This invention relates to a watercooler useful, for example, at home, an office, a store or any other work place, specifically to a watercooler of the type that water is chilled into cold water after once boiling it and a watercooler of the type that water is caused to evaporate, the resulting water vapor is condensed and the condensate is then chilled into cold water.
b) Description of the Related Art
To provide good cold drinking water without chlorine, trihalomethane and the like, active R&D work is under way in recent years on boiling-type watercoolers in which water is chilled into cold water after once boiling it and distillation-type watercoolers in which water is caused to evaporate, the resulting water vapor is condensed and the condensate is then chilled into cold water, leading to a variety of proposals.
FIG. 9 is a schematic construction diagram of a conventional boiling-type watercooler. Water 101 placed in a pot 100 is drawn out by a recirculating pump 102 through a bottom part of the pot 100, is delivered to a cold water/hot water selector valve 103, and is then recirculated selectively either through a cold water pipe 104 or a hot water pipe 105.
The cold water pipe 104 is covered at a portion of its outer periphery by a cooling block 106 made of a thermal conductor such as a metal. A thermoelectric module 107 is arranged with a heat-absorbing side thereof maintained in close contact with the cooling block 106. Heat-dissipating fins 108 are disposed in close contact with a heat-dissipating side of the thermoelectric module 107. A fan 109 is arranged in the vicinity of the heat-dissipating fins 108.
On the other hand, the hot water pipe 105 is covered at a part of its outer periphery by a heating unit 111 equipped with a built-in heater 110.
Underneath the bottom part of the pot 100, a service pipe 113 composed of a glass pipe extends via a service pump 112. This service pipe 113 also serves as a water level gauge which indicates the amount of the water 101 within the pot 100.
When preparing cold water in this boiling-type watercooler, the cold water/hot water selector valve 103 is first switched to a hot water side (as indicated by a dotted arrow), and the recirculating pump 102 is driven so that the water 101 is heated at the heating unit 111 while being fed through the hot water pipe 105. By repeating this recirculation, the temperature of the whole water 101 inside the pot 100 gradually rises and eventually reaches a boiling point, at which boiling is continued for a predetermined time (for example, 5 to 8 minutes). By this boiling, chlorine, trihalomethane and the like which are contained in the water 101 are removed from the inside of the pot 101 by an unillustrated removal unit.
After the boiling has been performed for the predetermined time, the heating unit 111 is deenergized and instead, the thermoelectric module 107 is energized and at the same time, the fan 109 is driven and the cold water/hot water selector valve 103 is switched to a cold water side (as indicated by a solid arrow). By recirculating the boiled water through the cold water pipe 104, the temperature of the boiled water gradually drops owing to the Peltier effect of the thermoelectric module 107. The water 101 eventually becomes cold water of an adequate temperature. Through the service pipe 113 the cold water can then be dispensed in an amount as much as needed.
The boiling-type watercooler is however designed to boil the water 101, which is filled in the pot 100, for the predetermined time while recirculating it and then to chill the water 101 down to a predetermined temperature while recirculating it. It is therefore impossible to dispense cold water until the water 101 has been chilled into cold water in its entirety. Obviously, a long time is needed until cold water becomes available. The boiling-type watercooler is therefore not suited where one wants to obtain cold water promptly.
Further, upon switching the cold water/hot water selector valve 103 to the cold water side and recirculating boiled water through the cold water pipe 104, a large thermal load is suddenly applied to the thermoelectric module 107. Thermal stress is hence exerted in the thermoelectric module 107, for example, on a solder layer joining heat-absorbing-side electrodes with semiconductor layers and also on a solder layer joining a heat-absorbing-side base with the heat-absorbing-side electrodes, whereby these solder layers may be damaged. As a result, the state of joining between these elements may be deteriorated, possibly leading to a drawback that the thermoelectric module 107 may have a short service life.